How can I duplicate a mesh along a curve?
Based on what you explained in the comments above, I think what you want are Dupliframes. My answer is based on the example in the wiki.

In short, you add a curve to the scene and in the Curve menu under Path Animation, you enable Follow. (You should also set the frames to a more reasonable number as needed such as 10 or so)



Then add the object and in the Object tab in the Properties Editor under Duplication enable Frames and disable Speed. 



Then parent the object to the curve or path, first select the object then the curve (so that the curve is the active object) and use Ctrl + P and Set Parent to Object. After, you can select the object and use Alt + O to reset its origin. 

Finally, you can now change the orientation of the object by either rotating it (either in Edit mode or Object mode). The arrangement of objects can, of course, be further enhanced by editing the curve. (Shaping it into text etc) 



Additionally from the same manual page linked above:


  There are many alternatives to Dupliframes. Which tool to use depends
  on context.
  
  
  To use a small curve as a profile and a larger curve as a
  path, simply use the former as a Bevel Object to the latter.
  To arrange objects along a curve, combining an Array Modifier and a Curve
  Modifier is often useful.
  Dupliverts can be used to arrange objects, for example, along a circle or across a subdivided plane.
  




Additionally, its worth noting that the additional objects are instances and not real objects, this will reduce the load of your scene and also allow you to be more flexible when adding more objects. Alternatively, you can Make Duplicates Real with Ctrl + Shift + A. All objects will now be real objects, but still linked copies. To change this, go to Object → Make Single User → Object &amp; Data and choose All.